I think it is hard to say who made this weight, and when.
Peter Von Brackel's 1999 book, Paperweights Historicism Art Nouveau Art Deco 1842 to Present covers lots of European weights of this general type and shows many with the flower stems as elongated air bubbles. In most cases they have been attributed as "Bohemian / Silesian/ Czechoslovakian" and dated to "1900-1930".
The leaves in this example could be seen as a "less common" feature, but they do occur in a number of examples.
I have always thought that the stems were made by inserting a thin tool downwards into the centre of the petals. Where the petals were originally set with a gap at the centre, the stem will be just a long clear bubble. But where the petals are set together, the colour of the petals will also then be seen in the stem.
Martin ... The "Eisner" examples I have seen are not like this one. They do not show a small "pot", but usually have a substantial "mound" which spreads across most of the view from above. Also, the stems in those weights have the same colour as the petals - and where multi-coloured petals are used, the stems also show the mix of colours. By the way, I know of no proven evidence that Frank Eisner worked at Moncrieff's in the 1930s. The initial information about this seems to be uncorroborated.
wrightoutlook ... I would be grateful to learn of any examples of this type of weight from Murano. Are there any images or details available via the internet or in the books? I am ware of versions with single flowers made with cane petals and set over a froth of bubbles. But I have not yet seen any that look like the regular early 20th century "Bohemian etc" output.